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See detailSatellite Broadband Capacity-on-Demand: Dynamic Beam Illumination with Selective Precoding
Chen, Lin UL; Lagunas, Eva UL; Chatzinotas, Symeon UL et al

in European Signal Processing Conference (EUSIPCO), Dublin, Ireland, Aug. 2021 (2021)

Efficient satellite resource utilization is one of the key challenges in next generation high-throughput satellite communication system. In this context, dynamic coverage scheduling based on traffic ... [more ▼]

Efficient satellite resource utilization is one of the key challenges in next generation high-throughput satellite communication system. In this context, dynamic coverage scheduling based on traffic demand has emerged as a promising solution, focusing system capacity into geographical areas where it is needed. Conventional Beam Hopping (BH) satellite system exploit the time-domain flexibility, which provides all available spectrum to a selected set of beams as long as they are not adjacent to each other. However, large geographical areas involving more than one adjacent beam may require full access to the available spectrum during particular instances of time. In this paper, we address this problem by proposing a dynamic beam illumination scheme combined with selective precoding, where only sub-sets of beams that are subject to strong inter-beam interference are precoded. With selective precoding, complexity at the groundsegment is reduced and only considered when needed. Supporting results based on numerical simulations show that the proposed scheme outperforms the relevant benchmarks in terms of demand matching performance. [less ▲]

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See detailTarzan and chain: exploring the ICO jungle and evaluating design archetypes
Bachmann, Nina M.; Drasch, Benedict; Fridgen, Gilbert UL et al

in Electronic Markets (2021)

The phenomenon of a blockchain use case called initial coin offering (ICO) is drawing increasing attention as a novel funding mechanism. ICO is a crowdfunding type that utilizes blockchain tokens to allow ... [more ▼]

The phenomenon of a blockchain use case called initial coin offering (ICO) is drawing increasing attention as a novel funding mechanism. ICO is a crowdfunding type that utilizes blockchain tokens to allow for truly peer-to-peer investments. Although more than \$7bn has been raised globally via ICOs as at 2018, the concept and its implications are not yet entirely understood. The research lags behind in providing in-depth analyses of ICO designs and their long-term success. We address this research gap by developing an ICO taxonomy, applying a cluster analysis to identify prevailing ICO archetypes, and providing an outlook on the token value market performance for individual archetypes. We identify five ICO design archetypes and display their secondary market development from both a short-term and a long-term perspective. We contribute to an in-depth understanding of ICOs and their implications. Further, we offer practitioners tangible design and success indications for future ICOs. [less ▲]

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See detailObserving Many Researchers Using the Same Data and Hypothesis Reveals a Hidden Universe of Uncertainty
Breznau, Nate; Rinke, Eike Mark; Wuttke, Alexander et al

E-print/Working paper (2021)

How does noise generated by researcher decisions undermine the credibility of science? We test this by observing all decisions made among 73 research teams as they independently conduct studies on the ... [more ▼]

How does noise generated by researcher decisions undermine the credibility of science? We test this by observing all decisions made among 73 research teams as they independently conduct studies on the same hypothesis with identical starting data. We find excessive variation of outcomes. When combined, the 107 observed research decisions taken across teams explained at most 2.6 of the total variance in effect sizes and 10 of the deviance in subjective conclusions. Expertise, prior beliefs and attitudes of the researchers explain even less. Each model deployed to test the hypothesis was unique, which highlights a vast universe of research design variability that is normally hidden from view and suggests humility when presenting and interpreting scientific findings. [less ▲]

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See detailHow Many Replicators Does It Take to Achieve Reliability? Investigating Researcher Variability in a Crowdsourced Replication
Breznau, Nate; Rinke, Eike Mark; Wuttke, Alexander et al

E-print/Working paper (2021)

The paper reports findings from a crowdsourced replication. Eighty-four replicator teams attempted to verify results reported in an original study by running the same models with the same data. The ... [more ▼]

The paper reports findings from a crowdsourced replication. Eighty-four replicator teams attempted to verify results reported in an original study by running the same models with the same data. The replication involved an experimental condition. A “transparent” group received the original study and code, and an “opaque” group received the same underlying study but with only a methods section and description of the regression coefficients without size or significance, and no code. The transparent group mostly verified the original study (95.5%), while the opaque group had less success (89.4%). Qualitative investigation of the replicators’ workflows reveals many causes of non-verification. Two categories of these causes are hypothesized, routine and non-routine. After correcting non-routine errors in the research process to ensure that the results reflect a level of quality that should be present in ‘real-world’ research, the rate of verification was 96.1 in the transparent group and 92.4 in the opaque group. Two conclusions follow: (1) Although high, the verification rate suggests that it would take a minimum of three replicators per study to achieve replication reliability of at least 95 confidence assuming ecological validity in this controlled setting, and (2) like any type of scientific research, replication is prone to errors that derive from routine and undeliberate actions in the research process. The latter suggests that idiosyncratic researcher variability might provide a key to understanding part of the “reliability crisis” in social and behavioral science and is a reminder of the importance of transparent and well documented workflows. [less ▲]

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See detailFrontrunner Jones and the Raiders of the Dark Forest: An Empirical Study of Frontrunning on the Ethereum Blockchain
Ferreira Torres, Christof UL; Camino, Ramiro; State, Radu UL

in USENIX Security Symposium, Virtual 11-13 August 2021 (2021)

Ethereum prospered the inception of a plethora of smart contract applications, ranging from gambling games to decentralized finance. However, Ethereum is also considered a highly adversarial environment ... [more ▼]

Ethereum prospered the inception of a plethora of smart contract applications, ranging from gambling games to decentralized finance. However, Ethereum is also considered a highly adversarial environment, where vulnerable smart contracts will eventually be exploited. Recently, Ethereum's pool of pending transaction has become a far more aggressive environment. In the hope of making some profit, attackers continuously monitor the transaction pool and try to frontrun their victims' transactions by either displacing or suppressing them, or strategically inserting their transactions. This paper aims to shed some light into what is known as a dark forest and uncover these predators' actions. We present a methodology to efficiently measure the three types of frontrunning: displacement, insertion, and suppression. We perform a large-scale analysis on more than 11M blocks and identify almost 200K attacks with an accumulated profit of 18.41M USD for the attackers, providing evidence that frontrunning is both, lucrative and a prevalent issue. [less ▲]

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See detailSuppression of the cooperative Jahn-Teller distortion and its effect on the Raman octahedra-rotation modes of TbMn1-xFexO3
Vilarinho, R.; Passos, D. J.; Queiros, E. C. et al

in PHYSICAL REVIEW B (2018), 97(14),

This work reports the changes in structure and lattice dynamics induced by substituting the Jahn-Teller-active Mn3+ ion by the Jahn-Teller-inactive Fe3+ in TbMn1-xFexO3 over the full composition range ... [more ▼]

This work reports the changes in structure and lattice dynamics induced by substituting the Jahn-Teller-active Mn3+ ion by the Jahn-Teller-inactive Fe3+ in TbMn1-xFexO3 over the full composition range. The structural analysis reveals that the amplitude of the 0 (pure 0.5, where it is completely suppressed. We then correlate this evolution with the behavior of the Raman modes across the solid solution. In particular, we show that the Raman modes associated with the rotation of octahedra, whose wave number is commonly considered to scale linearly with the tilt angles in orthorhombic Pnma perovskites are also sensitive to the amplitude of the Jahn-Teller distortion. [less ▲]

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See detailProfessional Careers of Retired Working Persons
Bisdorff, Raymond UL

in Diday, Edwin; Bock, Hans-Herrman (Eds.) Analysis of Symbolic Data: Exploratory methods for extracting statistical information from complex data (2000)

Illustrative benchmark analyses obtained in the context of social security statistics where professional careers of retired working persons from Luxembourg are analyses with the help of symbolic data ... [more ▼]

Illustrative benchmark analyses obtained in the context of social security statistics where professional careers of retired working persons from Luxembourg are analyses with the help of symbolic data analysis tools, like divisive symbolic clustering of professional careers and symbolic discriminant analysis of apparent retiring scenarios. [less ▲]

Detailed reference viewed: 34 (1 UL)